Office 365 - What are the limitations for message size, recipient number, and mailbox storage?

The specifications below outline the mailbox storage capacity limits as well as message and recipient size quotas associated with Office 365. Email usage data collected by the Administrative Excellence Phase II team suggest that only a very small percentage of campus users have email capacity needs beyond these limitations.

Important: The limits discussed below are set by Microsoft and cannot be controlled by UW-Madison administrators. For example, if you exceed the sent message daily limit, your account will be blocked from sending any further messages for a period of 24 hours.

Mail size quotas / caps:

Limit

Outgoing Messages

Outlook on the web

25 MB

Outlook 2016 or 2013 **

20 MB

Other desktop clients(Thunderbird, Apple Mail, etc) ***

25 MB

Incoming messages

All Clients

25 MB

** Client limits are set by Microsoft and cannot be altered by the Office365 team.

*** The Office 365 Technical Team is still in the process of determining whether there will be additional message size limitations for mobile devices. Some mobile clients may impose additional message or attachment size limits. These limitations can vary by device, client or settings selected.

These limits include all attachments, as well as the message itself. If an incoming message larger than 25 MB is sent to Office 365 recipient, the sender will receive a notification that the delivery has failed.